A novel two-step reduction process was constructed to removal nitrate selectively in aqueous solution. Nitrate was preliminarily reduced into nitrite with low yield of ammonia by microscale Cu/Fe bimetal, and then the accumulated nitrite was converted into N-2 by sodium sulfite. Cu was uniformly dispersed on the surface of Fe by a simple displacement reaction. Role of major iron components and fate of nitrogen species were investigated. The selectivity for N-2 was over 90%, and the yield of ammonia was below 10%. In the system, accumulation of nitrite resulted from the lower reduction rate of nitrite by Fe2+ in solution and the Cu/Fe coated by oxidized iron layer compared with the generation rate of nitrite via the reduction of nitrate. The generation of ammonia was caused by the reduction of nitrate/nitrite by Fe2+ adsorbed on the surface of oxidized iron layer coated on the bimetal at low reaction rate.